SPECIES OF GIBBON 571
compared with other Anthropoids is the fact of the large size of
the canines, which are of eq^ual or nearly equal size in the two
sexes. The molars on the other hand liave been particularly
FIQ. 272,—XIooloclc. llylobates hoolock. x J.
compared to those of Man. The brain is simpler than in the
higher forms. But it is not clear that this may not be a case
of diminished complexity of convolution going hand in hand
with smalliiess of size.
The Gibbons range through south-eastern Asia from Assam.
and Burmah to Hainan. The number of species is a little
doubtful. It is clear that in the first place we may distinguish
the Siarnang, JET. syndcwtylus, which indeed some regard as a
separate genus. It is mainly to be defined by the syndactylous
character of the second and third toes; they are united by skin
as far as the last joint. The Hainan species, JEL hainanus, is
probably distinct, and the following names have been given to
various other species or races, viz. H. agilis, J5T. leuciscus, If, leuco-
genys* JET. tar, H. hoolocTc. These animals can walk erect; and
when they do so, the big toe is separated as in no sophisticated
or at least unbooted man. The voice is well known to be loud,